This pronunciation is the cantonese version for the shanghainese "zǎnze"(长衫) , wich contrast with the mandarin chángshān(长衫), that is a term only for male clothes and QiPao(旗袍) for female clothes. But this dress , wich came from Manchuria, was used for the first time by "Han"(汉) women trough shanghainese students. Besides, ShangHai tailors fled to Hong Kong after Comunists Revolution in Continental China, and start to use chèungsàam for men and women. And QiPao[Kei Po](旗袍) became a more formal term.